A communication system may allow and handle numerous communication links that simultaneously exist and operate. However, one communication link may cause interference in another communication link, and vice versa. Interference can occur because two or more communication links use a same channel, while these communication links are geographically close to each other. Interference may also occur between communication links that use different channels. Channels may not be orthogonal in the sense that a signal in one channel can cause a residue in another channel, and vice versa.
In case a communication link experiences interference, this will adversely affect data transmission capacity and, therefore, transmission delay. In this respect, a level of interference relative to a data-carrying signal is an important parameter, which will be referred to as a relative level of interference hereinafter. The higher the relative level of interference that a communication link experiences, the lower the data transmission capacity will be and, therefore, the larger the transmission delay will be. In a communication system, there is a potential risk that one or more communication links have relatively low data transmission capacities and thus relatively large transmission delays due to interference. This can occur while one or more other communication links have relatively high data transmission capacities and thus relatively small transmission delays. In general, it is preferred to avoid such an unbalanced situation.
The relative level of interference that a communication link experiences from another communication link, and vice versa, may be balanced by applying a different parameter setting to the one or the other communication link, or both. The different parameter setting may concern one or more parameters of these communication links, such as, for example, transmission power, channel assignment, and geometrical location through access point assignment, whichever is applicable. However, the different parameter setting, which balances the relative levels of interference in the two aforementioned communication links, may affect other communication links: interference in these communications links may increase. That is, achieving a balance between two communication links may create an unbalance, or may amplify an unbalance, between two or more other communication links. Adjusting parameter settings so as to achieve a system-wide balanced state, which provides fairness in terms of transmission capacity and delay, is a complex problem, in particular if there are many communication links. Complexity tends to grow exponentially with the number of communications links.
The article entitled “MAPEL: Achieving Global Optimality for a Non-Convex Wireless Power Control Problem” by L. Qian et al. published in IEEE Transactions on Wireless Communications Wireless, Vol. 8, no. 3, pp. 1553-1563, March 2009 describes a centralized solution. This solution is highly complex and can only be applied offline, which makes it impractical.
The article entitled “Distributed Interference Compensation for Wireless Networks” by J. Huang et al. published in IEEE Journal on Selected Areas in Communications, Vol. 24, no. 5, pp. 1074-1084, May 2006 describes a distributed solution based on game theory. However, this solution provides no guarantee that a system-wide optimal state is achieved in terms of transmission capacity fairness and transmission delay fairness.